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Group E: Pure water group
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(a) Waters usually contain < 150 mg r 1 TDS, but may approach 20 - 40 mg r 1 in the
Pretoria quartzites.
(bl The Si0 2 content is generally high, especially in Old granite waters in the southern
Transvaal. The exception is water from the Table Mountain Series in the Cape
Province which approximates to the slightly saline Group B water.
(c) Moderately low chloride concentrations ranging from 8 -14% are evident, with the
exception of waters from the Table Mountain Series in Natal and the Cape
Province, and the Witteberg quartzites with> 30% Cl.
(d) In terms of the CaO : MgO ratio, MgO generally exceeds CaO.
(el Waters are slightly acidic with a pH just under 7,0.
(f) The waters are all very soft.
(gl Group E waters are those arising in sandstones and quartzitic rocks of the
Witwatersrand System, the Pretoria quartzites, Waterberg sandstones, the Table
Mountain Series in Natal and the Cape, and in the Old granite of the southern
Transvaal.
11.14.1 Some general observations regarding groundwater guality {according to Bond.
19461
(a) Ecca waters in northern Natal do not conform to any type.
(b) The most saline waters in South Africa - excluding the Pondoland (Transkei) Dwyka
springs which are rare - are those arising in the Old granite of the north west Cape
which have a mean TDS concentration of nearly 7 000 mg r 1 •
(cl The most alkaline waters in South Africa are those arising in the Upper Beaufort
and Stormberg sediments, and in some of the Pilansberg alkali rocks.